[PATCH v5 04/10] V4L: Add driver for s5k6a3 image sensor

[Sylwester Nawrocki]

Hi Baruch,

On 24/02/14 20:38, Baruch Siach wrote:
> On Mon, Feb 24, 2014 at 06:35:16PM +0100, Sylwester Nawrocki wrote:
>> > This patch adds subdev driver for Samsung S5K6A3 raw image sensor.
>> > As it is intended at the moment to be used only with the Exynos
>> > FIMC-IS (camera ISP) subsystem it is pretty minimal subdev driver.
>> > It doesn't do any I2C communication since the sensor is controlled
>> > by the ISP and its own firmware.
>> > This driver, if needed, can be updated in future into a regular
>> > subdev driver where the main CPU communicates with the sensor
>> > directly.
>> > 
>> > Signed-off-by: Sylwester Nawrocki <s.nawrocki at samsung.com>
>> > Acked-by: Kyungmin Park <kyungmin.park at samsung.com>
>
> [...]
> 
>> > +static int s5k6a3_open(struct v4l2_subdev *sd, struct v4l2_subdev_fh *fh)
>> > +{
>> > +	struct v4l2_mbus_framefmt *format = v4l2_subdev_get_try_format(fh, 0);
>> > +
>> > +	*format		= s5k6a3_formats[0];
>> > +	format->width	= S5K6A3_DEFAULT_WIDTH;
>> > +	format->height	= S5K6A3_DEFAULT_HEIGHT;
>> > +
>> > +	return 0;
>> > +}
>> > +
>> > +static const struct v4l2_subdev_internal_ops s5k6a3_sd_internal_ops = {
>> > +	.open = s5k6a3_open,
>> > +};
>
> Where is this used?

This will be called when user process opens the corresponding /dev/v4l-subdev*
device node. More details on the v4l2 sub-device interface can be found at [1],
[2]. The device node is created by an aggregate media device driver, once all
required sub-devices are registered to it.
The above v4l2_subdev_internal_ops::open() implementation is pretty simple,
it just sets V4L2_SUBDEV_FORMAT_TRY format to some initial default value.
That's a per file handle value, so each process opening a set of sub-devices
can try pipeline configuration independently. 

[1] http://linuxtv.org/downloads/v4l-dvb-apis/subdev.html
[2] http://linuxtv.org/downloads/v4l-dvb-apis/vidioc-subdev-g-fmt.html

Regards,
Sylwester